PROJECT SUMMARY Mammography remains an important diagnostic tool for breast cancer screening and diagnosis and has helped save thousands of lives. However, not every woman who gets routine screening is saved by mammography and an unacceptably large number of women are subjected unnecessary testing, biopsy and treatment due to false positives. Fischer Imaging has partnered with Johns Hopkins University to develop MammoCAT CT, a device for improved mammography in a comfortable, prone configuration where the breast is held without compression and will perform full field, computed tomography (CT) imaging at the same dose as standard full field digital mammography. This device will use slot-scanning CT technology (SSCT) that permits highly flexible sparse data acquisitions for reduced scan time and reduced x-ray exposure. To aid this effort we propose using novel reconstruction algorithms based on compressed sensing theory have achieved sparse data reductions of an order of magnitude or more. This combination of innovation in both hardware and software will help MammoCAT CT improve the sensitivity and specificity of mammography by improving image resolution and contrast and removing image artifacts due to tissue superimposition, all using similar x-ray dose as that of standard mammography. An important advantage of the prone configuration in MammoCAT CT is that it will allow precision biopsy and therapy by using the same high performance image feedback as mammography in a prone, comfortable setting. We believe MammoCAT CT will usher in a new era where every woman will benefit from mammography and where tumors can be detected, diagnosed and biopsied in the same device thus improving equipment and space utilization and improving hospital workflow.